The invention relates to a distilling apparatus, more particularly for distilling spent solvent in a dry cleaning plant for the solvent cleaning of articles such as garments, comprising a heating device, an inlet for medium to be distilled, a vapor outlet, a distilling space between the inlet for the medium to be distilled and the vapor outlet and a drain arranged in the bottom part of the distilling space and extending from it for the separated components.
The distilling apparatus is thus more particularly conceived for chemical, liquid solvents, which are utilized in the plant for dry cleaning. In the case of such a cleaning apparatus the dirt on the articles is dissolved in the solvent so that the latter becomes contaminated in the course of time with oil, fatty acids and the like. Such contaminants may be separated by process of distillation.
Distillation apparatus is also used for cleaning other liquids besides solvents, as for instance for preparing distilled water.
Such a still with the above specified features is described in the German unexamined patent specification 3,714,906.
In the still in accordance with this said specification 3,714,906 there are a number of vertical lengths of tube, which are arranged in the bottom part of the distilling space and each contain a heating electrode. The medium to be distilled is supplied to the lengths of tube via an inlet therefor at the bottom of the still so that the medium to be distilled flows through the tubes and is heated by the heating electrodes. The vapor emerging from the tubes is then deflected a number of times and arrives at the vapor outlet. The high boiling point fraction remains in the tubes and may be removed therefrom via a drain at the bottom.
This still suffers from various disadvantages.
The heating electrodes dip directly into the medium to be distilled so that the latter is heated around the respective electrodes to a substantially greater extent than at parts remote therefrom. In order to produce a heating effect so that the temperature which is at every point in excess of the evaporation point, the heating electrodes have therefore to be operated to produce an unnecessarily high heating effect, this is not only giving rise to increased operating costs but furthermore leading to local overheating of the medium to be distilled so that the latter may decompose if it is for instance in the form of a solvent.
Furthermore overheating leads to the formation of foam so that it will not only be vapor but also foam which emerges at the tubes. This is certainly also the reason for the adjoining vapor path having bends and further drain points. In this respect the upward motion and the emergence of the foam is favored by the use of a pump to supply the medium to be distilled and which forces it upwards. Owing to the flow path extending in an upward direction in the tubes it is not possible to dispense with this application of pressure.
Furthermore the still is a comparatively complicated piece of apparatus requiring much space since the local and direct heating of the medium to be distilled leads to the necessity of having a plurality of tubes, which each have to be provided with a heating electrode and the various ports. Added to this, there is provision of extra complexity and space requirement due to the path of the medium having to be changed, i.e. the flow path having to be deflected, a number of times.
A further substantial defect is that during the distillation phase the drain from the tubes has to be shut off. If this were not the case, the medium to be distilled would immediately escape from the still after entering the tubes, that is to say, there would be no distillation. The result is thus intermittent operation so that there are idle times in which the separated materials are let off. Intermittent operation furthermore means that the separated components may collect in the lower parts of the tubes and form solid deposits.